Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Jan 27th, 2020–Jan 28th, 2020

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Coast Inland.

The Coquihalla will see reactive new storm slabs develop overnight. In the north of the region, light amounts of new snow coupled with strong winds will continue to stress deep weak layers which have recently produced very large avalanches.

Confidence

Moderate - Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Weather Forecast

Monday night: Scattered flurries bringing 20 cm to the Coquihalla, 5-10 cm elsewhere. Alpine low -6 C. Strong southwest wind. Freezing level 1100 m.

Tuesday: Flurries in the morning, clearing to sun and cloud. Alpine high -1 C. Light southwest winds. Freezing level rising to 1500 m.

Wednesday: Flurries bringing up to 5 cm new snow. Alpine high 0 C. Strong souyhwest winds, approaching extreme at ridgetop. Freezing level 1600 m.

Thursday: Mix of sun and cloud with flurries in the evening. Alpine high -3 C. Light to moderate southwest wind. Freezing level 1100 m in the north, 1500 m in the south.

Avalanche Summary

Natural wind slab avalanches size 2-2.5 were observed on wind-loaded slopes in the alpine on Sunday. 

Several very large (size 3) deep persistent avalanches were reported to have failed naturally between late Thursday and Saturday, the reports come from around the Duffey Lake area and further north in the region towards Gold Bridge and Whitecap Mountain. These avalanches occurred on east, north, and west aspects around 2000-2200 m.

On Friday, skiers remotely triggered a size 3 avalanche on a north aspect at 2100 m in the Duffey area and a size 1 deep persistent avalanche while traveling along a skin track on a west aspect at 2050 m near Whitecap Mountain. 

Snowpack Summary

30-50 cm of recent snow sits over the January 20 crust up to 2000 m. At upper elevations, this snow has been redistributed by recent strong southwest winds. Below 1600 m, overnight snowfall rests on a crust.

There have been two layers of concern in the northern half of the region (e.g. Duffey, Hurley). One is a weak layer of surface hoar buried about 100 cm deep in sheltered areas around treeline. The other is weak basal facet crust complex. The latter has been the failure plane in recently reported deep persistent avalanches and is most likely to be triggered in shallow rocky start zones. There are currently no concerns about deep weak layers in the south of the region (e.g. Coquihalla).

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Be careful as you transition into wind affected terrain.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.